1)  Coal mining under buildings and railroads and water bodies
三下采煤
2)  "three unders" mining
“三下”采煤
1.
Yungang Mine is typical “three unders” mining district in which there is a big area together with water, railway and buildings.
云冈矿“三下”压煤面积大,且建筑物、水体、铁路连成一体,为典型的“三下”采煤。
3)  coal-mining under three circumstances
三下采煤理论
4)  "three beneath"
“三下”
1.
This paper discussed the preconditions for“three beneath”coal prospecting in the Longyan area,ana- lysed the possibility of prospecting coal by“three beneath”and listed several regions suitable for“three beneath” prospecting.
本文探讨了龙岩地区“三下”找煤应具备的一些先决条件,分析了“三下”找到煤炭的可能性大小, 并各举了若干比较符合条件的地区加以论述。
5)  three-underground mining
三下开采
6)  the Under-Three-Objects ore body
“三下”矿体
参考词条
补充资料：三下采煤
    　　建筑物下采煤、铁路下采煤、水体下采煤的总称。
　　

说明：补充资料仅用于学习参考，请勿用于其它任何用途。